China yesterday unveiled ambitious plans to improve its capital's heavily polluted air in time for the Olympics, including halting construction and heavy industry.

Beijing's Municipal Environmental Protection Bureau laid out a range of tough measures to cut back pollution, such as closing numerous petrol stations and even banning spray-painting.

The bureau's deputy director, Du Shaozhong, warned that even more "strident" measures would be taken if the weather was unfavourable by the time the games begin in August. The month is regarded as one of the worst in terms of pollution in the city because the air is humid and often stagnant.

Beijing is one of the most polluted cities in the world. But the authorities say they have invested £8.6bn to tackle the city's infamous smog - an unpleasant combination of carbon monoxide, sulphur dioxide, nitrogen dioxide and particulate matter of which much is produced by the building industry.

Since March, some types of construction work have been banned on windy days. But from July, all digging and pouring of concrete on sites will be suspended for two months.

Production will be stopped at cement, concrete mixing and cement grinding plants in south-east Beijing. Nearby quarries will also cease to operate.

About one in 10 petrol stations will be closed at the end of next month, while many more will be fitted with devices to reduce the level of fuel fumes they produce. Outdoor spray-painting will also be banned during the period, as will spraying or painting with "harmful solvents".

Construction of the Olympic venues is complete. But there are many private developments under way and the authorities are still working on major infrastructure projects - including subway lines and waterways - in the run-up to the games.

Last month the state news agency Xinhua reported that construction sites cover 100m sq metres (40 sq miles) of the capital - which is no surprise to residents, who are used to buildings being torn down and new ones erected at dizzying speed.

Nineteen heavy-polluting companies also have been told to cut their emissions by another 30% from July and coal-burning boilers that fail to meet emission standards will be closed.

Factories in areas surrounding the capital - including the city of Tianjin; the provinces of Hebei, Shanxi and Shandong; and the huge Inner Mongolia region - will also shut down during the summer.

Officials have not yet published their traffic plans, but are expected to ban about half of Beijing's 3.3m vehicles during the games to reduce pollution. They have also said they may encourage residents to take holidays, to reduce congestion.

But international teams competing in the Olympics are pursuing their own solutions in advance of the games in case organisers fail to meet the targets for air quality. The US has developed special masks for athletes which include a carbon filtration system.

Haile Gebrselassie, the world record-holder for the marathon, said in March that he would pull out of the Beijing race because he feared the pollution would damage his health. The Ethiopian runner, who suffers from asthma, may enter the 10,000 metres instead.

Jacques Rogge, the president of the International Olympics committee, has said he does not believe Beijing's air quality could endanger competitors' health - though he acknowledged their performance levels could be "slightly reduced".

IOC research released last month said conditions would "not necessarily [be] ideal at every moment", but added that the air quality was better than expected. The IOC has said it will postpone outdoor endurance events which take more than one hour if air quality is poor.